Center stable relay structure



March 10, 1970 1', KmzM ETAL 3,500,268

CENTER STABLE RELAY STRUCTURE Filed Jan. $1, 1969 izlfl fi linmnuml jfia-dare [fig imam 18 mmoms' United States Patent 3,500,268 CENTER STABLE RELAY STRUCTURE Theodore M. Krizman, Osceola, and Clayton M. Emmons, Elkhart, Ind., assignors to The Adams & Westlake Company, a corporation of Illinois Filed Jan. 31, 1969, Ser. No. 795,651 Int. Cl. H01h 51/28, 1/66 US. Cl. 335153 8 Claims ABSTRACT OF THE DISCLOSURE An electrical relay with the magnetic fiux from magnetic circuitry arranged to hold a switch armature between and out of contact with a pair of pole pieces. A magnetic flux conductor couples magnets associated with the armature stem and pole pieces to provide good operating sensitivity and a center stable nonenergized position. Flux from an electrical coil unbalances the permanent magnet flux to cause selective contact between the armature and one or the other of the pole pieces.

The present invention is directed to new and useful improvements in electrical relays and is particularly concerned with improvements which enhance the perform- .ance of center stable relays.

Electrical relays utilizing a movable switch armature between a pair of pole pieces in a glass envelope have been in widespread use for a number of years. In relays of this type magnetic flux from an electrical coil associated with the switch causes the armature to move into selective contact with one or the other of the pole pieces of the switch. Various permanent magnet circuits and armature spring arrangements have been devised for switches of this type so as to provide contact between the armature and a contact face of one pole piece when the operating coil is deenergized. Relays of this type may be center stable. The term center stable as used herein refers to a switch construction of this class in which the armature has a neutral position between and out of contact with both pole pieces of the switch in the absence of magnetic flux from the coil, and in which the armature may move into contact with one or the other of the pole pieces, depending upon the polarity of electrical flux created by the electrical coil associated with the relay.

The major purpose of the present invention is to so arrange a permanent magnetic circuit in relays of this general center stable type that, when used with an electrical coil, a sensitive switch is provided and in which the out-of-contact relation between the switch contact elements can be maintained easily without requiring any more manufacturing cost in assembling the contact elements within the glass envelope than is necessary in relays of the single side stable or bistable form. Relays incorporating the principles of the present invention may have the contact elements relatively closely spaced without undesired contact bounce between the armature and contacts of the pole pieces.

These and other purposes will become more apparent in the course of the ensuing specification and claims when taken with the accompanying drawings, in which:

FIGURE 1 is a front elevational view of a typical center stable relay incorporating the principles of the present invention;

FIGURE 2 is a side view of the relay illustrated in FIGURE 1;

FIGURE 3 is a rear view of the relay illustrated in FIGURES 1 and 2 and partially in section to illustrate the relation of the switch contact elements; and

FIGURE 4 is a top view of the relay illustrated in FIGURES 1, 2. and 3.

CTl

3,500,268 Patented Mar. 10, 1970 Like elements are designated by like characters throughout the specification and drawings.

With specific reference now to the drawings and in the first instance to FIGURE 1, the numeral ltl generally designates a switch of conventional form. The switch is defined by an armature 11 positioned within a glass or glass-like envelope 12 and by a pair of pole pieces 13 and 14 which have contact faces 13a and 14a within the envelope and positioned on opposite sides of the free end of the armature. The armature is mounted within the glass envelope for swinging movement into contact with one or the other of the contact faces 13a and 14a of the pole pieces 13 and 14, respectively. The armature stem 15 extends outwardly from one end of the envelope while the pole pieces extend outwardly in generally parallel relation from the other end of the envelope. Switches as thus generally defined are known to the art and are described in a number of patents and publications including United States Patent No. 2,609,464 and United States Patent No. 3,054,873, the switch disclosures of which are hereby incorporated by reference. In switches of this type, a body of mercury may be provided within the glass envelope so that the armature and contact faces of the pole pieces are kept wetted with mercury through capillary action. The pole pieces and armature are formed from a magnetic material such as a nickel-iron alloy.

In accordance with the invention, a permanent magnet 16, which may take the form of a cylindrical magnet with defined magnetic poles at opposite ends thereof is positioned adjacent to the exterior end portions of both pole pieces 13 and 14. The magnet 16 is positioned so that both pole pieces 13 and 14 assume the same mag netic polarity, as for example a north polarity under influence of the permanent magnet 16. The end face of the magnet 16 is in close proximity to both pole pieces 13 and 14 but it is spaced slightly therefrom. A rectangular sheet of insualting material 17 may be positioned between one pole piece 14 and the magnet to insure the spaced relation and electrically insulate the magnet from one pole piece. Another permanent magnet 18, which may also be cylindrical in form, is fixed to the exposed armature stem 15 and positioned in such a Way that the armature stem assumes the same polarity as that of the polarity imparted to the pole pieces 13 and 14 by the permanent magnet 16. Again this may be accomplished by placing the north pole of magnet 18 adjacent and in contact with the armature stem 15.

With the magnets thus positioned, the contact faces of the pole pieces have the same polarity as the armature 11 and with the same polarity, the armature is repelled equally by the two contact faces. The resultant magnetic forces hold the armature in a position between and spaced from each of the contact faces of the pole pieces.

In order to operate the relay and cause selective contact of the armature with one or the other of the contact faces 13a and 14a and thus close a circuit through a selected pole piece, an electrical coil 19 is associated with the pole pieces so as to impart electrical flux of a selected polarity to the pole pieces. As shown, the coil 19 is positioned above the pole pieces and is supported therefrom by magnetic circuit members 20 and 21 which are fixed to the ends of the coil and also fixed to the pole pieces. One member 20, for example, is fixed to one end of the coil 19 and to the pole piece 13 while the other member 21 is fixed to the other pole piece 17 and fixed to the other end of the electrical coil. The ends 20a and 21a of the members 20 and 21 extend within the coil 19 to form a magnetic core for the coil. These ends are electrically insulated from one another. One member, as for example member 21, should be insulated from the coil and other member and this is accomplished by means of an electrical insulating strip 211: which surrounds the end 21a of the member 21 with the end of the coil. By operating the coil with direct current, one end of the coil will become a north pole and the other end of the coil will become a south pole and the magnetic circuit members associated with the ends of the coil assume a like polarity with their associated ends of the coil. For example, if the end of the coil 19 with the member 20 is a north pole, this provides electrical flux of north polarity to pole piece 13 while the opposite end of the coil provides electrical flux of south polarity to pole piece 14. The coil has a size such, that with relation to the electrical current supplied to it, the electrically imposed flux of south polarity imposed on pole piece 14 is greater than the permanent magnet north polarity of the pole piece. The south polarity overcomes the north polarity of pole piece 14 While the electrical flux aids the north polarity of pole piece 13. This causes an even greater repulsion of armature 11 by pole piece 13 and an attraction of armature 11 by pole piece 14 causing armature 11 to move into contact with the contact face 14a of pole piece 14 and close the circuit through that contact face. When the coil is denergized, the permanent magnet flux will again cause both contact faces to repel armature 11 so that the armature 11 again assumes a center stable position. When the current to the coil is reversed, the polarities at the ends of the coil are also reversed and reversal of current to the coil causes the armature 11 to contact the other contact face, as for example, contact face 13a to complete the electrical circuit through pole piece 13.

In further accordance with the invention, the sensitivity of the relay is increased by magnetically coupling the two permanent magents 16 and 18. This is accomplished through use of a coupling strap which may be of a nickel-iron alloy or steel possessing low reluctance. Strap 22 is welded or otherwise ailixed to one magnet, as for example magnet 16, and is fixed to the outer end of the other magnet 18 with electrical insulation 22a between the strap 22 and the magnet 18. This couples the poles of like polarity of magnets 16 and 18 together and in effect produces an action similar to having a south pole or a pole of the same polarity as the outer ends of magnets 16 and 18 all along the length of the strap 22. This is believed to have the effect of increasing the strength of the polarity of the armature 11 which is opposite to that of the strap 22. Magnetic flux lines will appear as indicated at F in FIGURE 2, that is, lines transversely to the length of the armature 11 and to thelength of the strap 22, thus increasing the sensitivity of the relay.

Use of the strap 22 between the magnets 16 and 18 may increase the sensitivity of the relay by approximately 40% over and above relays not using such a strap but otherwise using the same magnet positioning and coil structure. The increase in sensitivitydecreases the amount of current required to move the armature in one direction or the other.

Through use of the principles set forth herein, the contact faces of the relay may be relatively close together and relatively close to the swingable armature and the armature will nonetheless remain in a center stable or oit position. The pole pieces and armature may be assembled in the enevelope in the same manner as other relays. Contact bounce of the armature may be eliminated if the armature is mercury wetted.

We claim:

1. An electrical relay including a glass-like envelope having a movable contact element positioned therein for selective movement into and out of contact with another contact element therein, said other contact element extending beyond one end of said envelope, said movable contact element having a stem extended beyond the end and exteriorly of the other end of said envelope, permanent magnet means associated with the exterior portions of both elements so as to create the same magnetic polarity for the contact portions of both elements, and an operating electrical coil associated with one of said contact elements and effective when energized to reverse the polarity of that contact element.

2. The structure of claim 1 characterized by and including a strip of low reluctance material extending adjacent to said envelope and generally parallel to the longitudinal axis thereof, and means imparting a polarity to said strip opposite to the permanent magnet polarity of said contact elements.

3. The structure of claim 1 characterized by and including a permanent magnet in contact with the exterior portion of said movable contact element and a permanent magnet associated with the exterior portion of said other contact element, said permanent magnets each providing the same polarity for the contact elements.

4. The structure of claim 3 characterized by and including a strip of low reluctance material extending generally parallel to the axis of said envelope and exteriorly thereof, said strip being magnetically associated with the poles of said permanent magnets which are opposite to the polarities of said contact elements.

5. A center stable relay including a glass-like envelope having an armature positioned between contact faces of pole pieces at one end of said envelope, said pole pieces extending beyond one end of said envelope, said armature having an armature stem extended beyond the end and exteriorly of the other end of said envelope, permanent magnet means associated with each pole piece and said armature stem so as to create the same magnetic polarity for the contact portion of the armature and the contact faces of the pole pieces, a strip of low reluctance material positioned exteriorly of and adjacent to said envelope and extending generally parallel to said envelope and armature, means providing a polarity for said strip of material opposite to the polarity of said armature and pole pieces, and an operating electrical coil associated with said relay so that when energized, the polarity of a selected pole piece is caused to be opposite to the polarity of said armature.

6. The structure of claim 5 characterized by and in cluding a permanent magnet in contact with said armature stern and permanent magnet means associated with said pole pieces, said permanent magnet and permanent magnet means each'providing the same polarity for the armature stem and the pole pieces.

7. The structure of claim 5 wherein said strip extends between said permanent magnet and said permanent magnet means and is associated with poles of said permanent magnet and permanent magnet means which are opposite in polarity to the polarity of said pole pieces and armature.

8. The structure of claim 5 wherein said coil is positioned adjacent the ends of the pole pieces exterior to said envelope and is supported by magnetic coupling members fixed to the pole pieces and extended within the coil.

References Cited UNITED STATES PATENTS 3,254,327 5/1966 Freimanis et al. 335l53 X 3,324,430 6/1967 De Lucia 335153 X BERNARD A. GILHEANY, Primary Examiner R. N. ENVALL, JR., Assistant Examiner 

